Polyurethane foam is produced by mixing isocyanate, polyol, and water to create two simultaneous reactions: a gelling or polymerization reaction and a blowing or gas-producing reaction. The gelling reaction occurs when the isocyanate reacts with the polyol to form urethane chains. The blowing reaction occurs when the isocyanate reacts with the water to form carbon dioxide gas. The urethane chains make up the structure of the foam, while the carbon dioxide gas creates porosity within the foam by expanding the polyurethane polymer. Numerous additives may be mixed with the isocyanate, polyol, and water to control the rate and duration of the gelling and blowing reactions, while also providing a mechanism for urethane chain cross-linking and chain extension. By controlling the rate and duration of the gelling and blowing reactions, the polyurethane foam production facility can control the physical properties of the foam such that the resultant product has a desired set of characteristics. When the gelling and blowing reactions are completed and the foam has had sufficient time to fully cure, the resulting polyurethane foam bun may be processed into various polyurethane foam products.
It is desirable for the resultant foam product to have certain advantageous properties. For example, the foam may be required to be substantially white with little to no yellowing. Additionally, depending on the end-use application, the foam may be required to have substantially no odor associated with it. It is also preferable that the foam minimize its volatile organic compound (VOC) content or emissions. Finally, it is advantageous for the foam to be made from renewable energy sources so that the foam can be marketed as environmentally friendly or “green.”